The Life History of Pyrroloquinoline Quinone (PQQ): A Versatile Molecule with Novel Impacts on Living Systems

Pyrroloquinoline quinone (4, 5-dihydro(4), 5-dioxo(1) H-pyrroloquinoline-2,7, 9 tricarboxylic acid) being a three ortho cyclic quinone substitutes the role of a redox-cofactor for various bacterial dehydrogenases such as methanol, ethanol and glucose dehydrogenases [1-6] also termed as methotaxin [7]. PQQ structure prediction shows that it has been originated from tyrosine and Glutamic-acid [8] but the pathway for PQQ biosynthesis is whist in process of identification [9]. PQQ being involved in Gluconic acid production and biosynthesis by microbes. GDH-A and GDH-B (s-GDH) are soluble enzymes [10]. PQQ synthesizing operon containing 6-7 genes i.e. (pqqABCDEF/G) [11,12] and orientation effects [13] and biocatalysis are carried by bioelectric oxidation of glucose into gluconic acid [14]. It acts as potent microbial growth stimulant and diversified role in antibiotics as chief biological control determinant for plant pathogens [15]. PQQ-GDH has role in direct electron transfer of bacterial energy transduction and ATP synthesis during oxidation [16,17]. The soluble membrane bound serine and threonine kinases repair damage of DNA by radiation [18]. PQQ has diverse roles in animals like NMDA mediated receptor in neurological injury, repair and improved memory by ERK1/2 pathway pathway [19]. PQQ is a powerful anti-melanogenic agent and quite effective against disorders related to hyper pigmentation [20]. It plays role in MAPk kinase activation and tyrosyl phosphorylation of ERK2 by production of CD4+ T lymphocytes [21]. PQQ promotes and improves neonatal development and reproduction involving mitochondrial biogenesis and cell signaling pathways [22]. PQQ plays vital role in liver fibrogensis [23] and in signal transduction via mitochondrial biogenesis [24]. It has diverse functions in insulin resistance and aging by creation of new mitochondria [25].